Change the proposed GC algorithm for the global heap.

Documentation/chap-garbage-collection.tex

@@ -17,8 +17,7 @@ relative age of the objects, so that we can promote only the oldest
 objects when required. 
 
 In addition to the thread-local heaps, there is a global heap.  The
-garbage collector for this heap will use the method invented by
-Kermany et al \cite{Kermany:2006:CCI:1133981.1134023}.  It is also a
-sliding garbage collector, except that it has some very good features,
-including parallel and concurrent execution.  These features allow us
-to run the global garbage collector in multiple separate threads. 
+garbage collector for this heap will use a combination of the
+traditional \emph{mark-and-sweep} collector and an ordinary memory
+allocator, similar to the one used by the \clanguage{} functions
+\texttt{malloc} and \texttt{free}.